Process for producing petrol of high octane number by catalytic reforming and a reactor for carrying out this process

ABSTRACT

The invention relates to a process for producing petrol of high octane number by catalytic reforming of hydrocarbons by passing these hydrocarbons through a platinum/rhenium catalyst arranged in the form of a hollow cylinder at 450°-500° C. and a pressure of 1.5-3 MPa in a direction perpendicular to the cylinder axis, in which the feed mixture is passed through in the direction from the cylinder axis to the circumference thereof. The invention further relates to a reactor for carrying out the process mentioned, in particular as shown in FIG. 1.

This is a nationalization under 35 U.S.C. § 371 of PCT/EP94/02932, filedSep. 2, 1994.

BACKGROUND OF THE INVENTION

The invention relates to the field of petroleum processing orpetrochemistry, concretely processes for processing hydrocarbons andapparatus for carrying them out, in particular to motor fuels as aredescribed in Ullmann's Encyclopedia of Industrial Chemistry, Vol. A 16,Verlag Chemie Weinheim, 1990, pp. 719-753; the entire contents of thispublication are hereby incorporated by reference.

Catalytic reforming is generally a refining step in petrochemistry, inparticular the thermal and/or catalytic conversion of certain petroleumproducts, in particular heavy naphthas and so-called straight-runpetrols, into aromatics and isoparaffins. The purpose of reforming is toincrease the octane number of motor fuels and also to obtain byproductssuitable for the chemical industry, such as the BTX fraction. Thedetails of reforming are well documented; reference is here made only byway of example to Ullmann's Encyclopedia of Industrial Chemistry, Vol. A18, Verlag Chemie Weinheim, 1991, pp. 51-99, in particular pp. 67-70(Catalytic Reforming).

E. V. Smidovich, Tekhnologya pererabotky nefty i gaza, "Khimya"publishers, Moscow, 1968, part 2, pp. 243-245 (1) discloses a processfor producing petrol of high octane number by catalytic reforming ofpetrol fractions of low octane number at temperatures of 500°±50° C. anda pressure of up to 3.5 MPa with dilution of the feed mixture by acirculated hydrogen-containing gas in an amount of 1500 standard m³/standard m³ of feed mixture at a molar concentration of hydrogen in thehydrogen-containing circulated gas of at least 75% in the presence of analumino platinum catalyst having a metallic platinum content of at most0.63% at a space velocity of the feed mixture of from 1.5 to 1.8standard m³ /standard m³ of catalyst.

The starting mixture and the steam/gas mixture are passed through thecatalyst bed parallel to the vertical axis (axially) of the reactorwhich is a verti cal cylindrical vessel having an axial, fully metallictube for drawing off a gaseous product mixture and a perforated metallicinsert arranged therein, with a catalyst bed being located between thewalls of the insert and the central tube.

However, this process for producing petrol of high octane number has thefollowing disadvantages:

1. high hydraulic losses when the steam/gas mixture passes through thecatalyst bed, owing to a high linear flow velocity because of thelimited effective cross-sectional area of the catalyst bed;

2. the presence of catalyst dust which, under the process conditions,collects at the outlet of the gaseous product mixture from the catalystbed and reduces the effective cross-section;

3. increased pressure in the system which shifts the chemical conversionof the hydrocarbon starting material in the direction of the formationof low-value reforming products (byproducts); the proportion ofhydrocracking products increases.

As regards its technology, the process of the invention comes closest toa process disclosed in Khimya i tekhnologya topliv i masel, "Khimya"publishers, Moscow, 1966, No. 3, p. 14 (2) for producing petrol of highoctane number by catalytic reforming of a mixture of hydrogen andhydrocarbons by passing this mixture through a platinum/rhenium catalystarranged in the form of a hollow cylinder at 450°-500° C. and a pressureof 1.5-3 MPa. The feed mixture flows in the direction from thecircumference of the reactor to the axis thereof. The platinum/rheniumcatalysts used in this process are known and commercially available.

The petrol of high octane number is produced by catalytic reforming ofpetrol fractions of low octane number at a temperature of 450°-500° C.and a pressure of 2.8 to 5.0 MPa with dilution of the feed mixture byhydrogen-containing circulated gas in an amount of 1500 standard m³/standard m³ of feed at a molar concentration of the hydrogen in thehydrogen-containing circulated gas of 85% (the molar ratio of hydrogento feed is generally 8:1) in the presence of the platinum/rheniumcatalyst having a metallic platinum content of 0.30-0.65% at a spacevelocity of the feed mixture of 1.5-1.8 m³ /h per m³ of catalyst.

The disadvantages of this process are:

1. insufficient yield of product--up to 93.86% (cf. Example 1 whichreproduces the prior art);

2. the low octane number of the product--77.2 MON (motor octane number).

SUMMARY OF THE INVENTION

The invention relates to a process for producing high-octane petrol bythe catalytic reforming of hydrocarbons by taking said hydrocarbonsthrough a platinum-rhenium catalyst in the shape of a hollow cylinder at450°-500° C. and a pressure of 1.5-3 MPa in a direction perpendicular tothe cylinder axis, in which the inserted mixture passes from the axis tothe periphery of the cylinder. The invention also relates to a reactorfor implementing said process, especially in accordance with FIG. 1.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an overall view of the reactor.

FIG. 2 shows a view of the internal wall 7 of the insert 5.

FIG. 3 shows an embodiment of the insert 5.

FIG. 4 shows an embodiment of the insert 5 in which the internal wall 7has a conical shape.

FIG. 5 shows an embodiment of the insert 5 in which the internal wall 7is, viewed in axial section, in the form of steps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is an object of the invention to increase the yield of product ofhigh octane number and to improve the quality thereof.

This object is achieved by the present invention.

In a process for producing petrol of high octane number by catalyticreforming of a mixture of hydrogen and hydrocarbons by passing thismixture through a platinum/rhenium catalyst arranged in the form of ahollow cylinder at 450°-500° C. and a pressure of 1.5-3 MPa in adirection perpendicular to the cylinder axis, the feed mixture is,according to the invention, passed through in the direction from thecylinder axis to the circumference thereof.

The feed mixture preferably flows at a space velocity of 1.5-1.8 h⁻¹.

The volume ratio of hydrogen-containing gas to the hydrocarbons(hereinafter: "flow factor") is preferably 1200-1800 standard m³/standard m³ of HC (HC=hydrocarbon).

The above-specified features of the invention achieve the followingtechnical effect.

In the reactions possible over the catalyst, the equilibrium is shiftedin the direction of an increase in the percentage yield of cyclopentanesand isoparaffins, with at the same time the amount of aromatichydrocarbons being reduced slightly and the yield of gaseous materialsdecreasing (which leads to an increase in the stability of thecatalyst). This results from the fact that, in contrast to the closestprior art, in the process of the invention the feed mixture first comesinto contact with a relatively small amount of catalyst, which amountincreases along the further flow path of the feed mixture through thecatalyst bed with simultaneous alteration of the composition of the feedmixture.

If the feed mixture is passed through the catalyst bed at a spacevelocity of less than 1.5 h⁻¹, the composition of the catalyst is onlyslightly different from that in the prior art as described in (2),namely by a maximum of 3-5%.

However, if the feed mixture is passed through the catalyst bed at aspace velocity of >1.8 h⁻¹, the reactor is not able to completelyprocess the feed mixture.

If the flow factor is less than 1200 standard m³ /standard m³ of HC, thecoke yield increases.

If the flow factor is more than 1800 standard m³ /standard m³ of HC, theamount of iso-hydrocarbons and cyclic hydrocarbons decreases slightly(by 3-5%).

The process of the invention is distinguished from that described in (2)by the feed mixture being passed through the catalyst bed in thedirection from the axis of the cylinder to the circumference thereof.The process of the invention thus meets the inventive criterion of"novelty".

The technical scientific literature and the patent literature havehitherto not described any process for catalytic reforming in which thestarting mixture flows in the direction from the axis of a cylindricalcatalyst to the circumference thereof. The process of the invention thusmeets the inventive criterion of "an inventive step".

The process of the invention can be applied in the petrochemical andpetroleum processing industry; it allows the yield of petrol of highoctane number to be increased and the quality thereof to be improved.The process of the invention thus meets the inventive criterion of"industrial usefulness".

The process of the invention can be carried out with the aid of afurther invention, namely a reactor for catalytic reforming.

There is known a reactor for producing petrol of high octane number bycatalytic reforming, comprising a housing having ports for the entry ofthe feed mixture and for the exit of catalyst, a hollow insert arrangedin the housing clear of the external wall and of the internal surface ofthe housing and having an internal and an external wall which arearranged coaxially and provided with openings, with both ends of theinsert being fitted with covers, of which one is in the form of anannulus and is arranged between the internal surface of the housing andthe internal wall of the insert while the second cover is circular inshape and the end of the insert is able to be completely covered (2).

This reactor is not suitable for carrying out the process of theinvention, since in it the gas flows from the circumference of thereactor to the centre.

In a reactor for producing petrol of high octane number by catalyticreforming, comprising a housing having ports for the entry of the feedmixture and for the exit of catalyst, a hollow insert arranged in thehousing clear of the external wall thereof and the internal surface ofthe housing and having an internal and an external wall which arearranged coaxially and provided with openings, with both ends of theinsert being fitted with covers, of which one is in the form of anannulus and is arranged between the internal surface of the housing andthe internal wall of the insert and the other cover is circular in shapeand the end of the insert is able to be completely covered, according tothe invention the annular cover is fitted to the end nearest the entryport for the feed mixture while the circular cover is fitted to the endnearest the exit port for the catalyst.

The internal wall of the insert can be cylindrical in shape, with itsopenings being arranged in such a way that the distance between themdecreases in the direction of the axis of the insert from the endnearest the entry port for the feed mixture to the other end. Thedistance between the openings can decrease by a factor of 1.2-2.5.However, the diameter of the openings remains constant.

The internal wall of the insert can have a diameter which increases inthe direction of the axis of the insert from the end thereof nearest theentry port for the feed mixture to the other end.

The internal wall of the insert can, in particular, be conical or,viewed in axial section, in the form of steps.

According to a preferred embodiment of the invention, the internal wallof the insert can, viewed in axial section, be stepped in such a waythat the axial cross-sectional area of the steps increases in thedirection of the axis of the insert from the end thereof nearest theentry port for the feed mixture to the other end. In particular, theaxial cross-sectional area can increase by a factor of 1.2-2.5.

The covers mentioned can consist of two or more parts.

The above mentioned arrangement of the covers allows the gas stream toflow from the center of the reactor towards the circumference. Theconstruction of the internal wall of the insert with a diameter whichincreases in the direction of the axis of the insert allows constanthydrodynamic conditions for the entry of the gas into the reactor to bemaintained along the entire length of the insert.

The two-part construction of the covers makes maintenance of the reactorconsiderably easier.

The reactor of the invention is distinguished from that described in (1)by the annular cover being arranged at the end nearest the entry portfor the feed mixture, while the circular cover is fitted to the endnearest the exit port for the catalyst. The apparatus of the inventionthus meets the inventive criterion of "novelty".

In the technical scientific literature and the patent literature, thearrangement of the invention of covers for a reactor for catalyticreforming is not described. Thus the apparatus of the invention meetsthe inventive criterion of "an inventive step".

The apparatus of the invention can be used in the petrochemical andpetroleum processing industry; it allows an increase in the yield ofpetrol of high octane number and also an improvement in the petrolquality. The apparatus of the invention thus meets the inventivecriterion of "industrial usefulness".

An embodiment of the reactor of the invention is shown in FIGS. 1 to 5.

FIG. 1 shows an overall view of the reactor. The reactor comprises ahousing 1 having flanges 2 and 3 which have openings for the entry ofthe feed mixture or the exit of the catalyst. In the housing 1 there isarranged at a clearance 4 a hollow insert 5 which has an external wall 6and an internal wall 7 which are provided with openings 8 and 9respectively. The external wall 6 has a cylindrical shape. In FIG. 1,the internal wall 7 likewise has a cylindrical shape. Between the walls6 and 7 there is arranged a platinum/rhenium catalyst 10. Between theinternal surface of the housing 1 and the internal wall 7 of the insert5 there is arranged an annular cover 12 which, for ease of installation,is made up of two parts (it consists of the annular part 12 which coversthe intermediate space 4 and the annular part 14 which covers a part ofthe end of the insert between the walls thereof). The reactor housinghas openings 16 for the discharge of catalyst.

The circular cover 11 is fitted to the other end of the insert 5 andcovers this end completely. The reactor housing has ports 16 for thedischarge of catalyst. The reactor has an annular cover 12 havingopenings 13 for the exit of the steam/gas mixture. The reactor also hasflanges 15 and 16 for input and discharge of catalyst.

FIG. 2 shows a view of the internal wall 7 of the insert 5 havingopenings 9 of the same diameter, between which openings the distance lchanges from l₁ to l₂, where l₁ /l₂ =1.2-2.5 (e.g. from 75 to 40 mm at adiameter of 15 mm for each hole).

FIG. 3 shows an embodiment of the insert 5, in which the internal wall 7has a diameter which increases in the direction of the axis 18 of theinsert from the end nearest the port 2 for the entry of the feed mixtureto the other end.

FIG. 4 shows an embodiment of the insert 5 in which the internal wall 7has a conical shape (here the widening is from the inlet 2 for the feedmixture to the opposite end).

FIG. 5 shows an embodiment of the insert 5 in which the internal wall 7is, viewed in axial section, in the form of steps. Here, the diameterand the length of the steps increase in the direction of the axis 18 ofthe insert from the end thereof nearest the entry port 2 for the feedmixture to the other end. The axial cross-sectional area of the stepsincreases in such a way that S₂ /S₁ =1.2-2.5.

The reactor operates in the following way.

The ports 15 and 16 are opened and the required amount of catalyst isintroduced between the walls 6 and 7 of the insert 5. The ports 16 and18 are then closed.

The catalyst is dried in a stream of inert gas having a temperature ofup to 250° C. over the course of several hours. The inert gas isgradually replaced by a hydrogen-containing gas which is likewise fed inat a temperature of 250° C. The catalyst is reduced. Subsequently, ahydroxychlorination is carried out to activate the catalyst. Thecatalyst is now ready for service. At 250° C., the addition ofhydrocarbon feed to the circulated gas is then commenced withsimultaneous raising of the entry temperature to the processtemperature. The steam/gas mixture flows through the entry port 2,enters the interior of the insert, flows through the openings 9 of theinternal wall 7 and then through the catalyst bed 10 where it issubjected to chemical reactions, subsequently flows through the openings8 in the wall 6 into the intermediate space 4 and from there through theopenings 18 of the cover 12 and finally leaves the reactor via the exitport 3. Exactly this flow direction of the gas/steam mixture is ensuredby the covers 11, 12 and 14.

The examples below illustrate the process of the invention.

EXAMPLE 1

(comparison in accordance with the nearest prior art)

The process is carried out in the reactor 1 under the followingconditions.

    ______________________________________    Entry temperature of the mixture                         494° C.    of hydrogen and hydrocarbons    Exit temperature of the mixture                         450° C.    Pressure in the reactor                         3 MPa    Flow factor          1475.5 standard m.sup.3                         of hydrogen-con-                         taining gas per                         standard m.sup.3 of                         hydrocarbon    Molar ratio of hydrogen/hydro-                         8:1    carbons    Hydrogen concentration in the                         80%    gas    Space velocity       1.524 h.sup.-1.    ______________________________________

The composition of the feed mixture and the product at the reactoroutlet are shown in Table 1.

                                      TABLE 1    __________________________________________________________________________    Composition (kmol/h)    Steam     H.sub.2                  Dry gas                      Aromatics                           Napthenes                                n-paraffins                                     iso-paraffins    __________________________________________________________________________    Feed mixture on entry              9522.32                  2531.25                      105.4336                           338.5622                                292.1307                                     505.05    into the 1st reactor    Gas mixture at the exit              9827.56                  2624.85                      424.2                           125.23                                283.74                                     499.82    of the 1st reactor    __________________________________________________________________________

The product drawn off from the 1st reactor is fed to the 2nd reactorwhich is operated under the following conditions.

    ______________________________________           Entry temperature                     496° C.           Exit temperature                     473° C.    ______________________________________

The other operating conditions correspond to those in the precedingreactor. The composition of the feed mixture and the product on leavingthe 2nd reactor is shown in Table 2.

                                      TABLE 2    __________________________________________________________________________    Composition (kmol/h)    Steam     H.sub.2                  Dry gas                      Aromatics                           Napthenes                                n-paraffins                                     iso-paraffins    __________________________________________________________________________    Feed mixture on entry              9827.56                  2624.85                      424.2                           125.23                                283.74                                     499.82    into the 2nd reactor    Gas mixture at the exit              9931.3                  2745.26                      476.68                           71.00                                272.4                                     496.8    of the 2nd reactor    Gas mixture at the              9373.6                  2749.01                      467.33                           97.7 284.9                                     504.0    reactor exit after    reconstruction    __________________________________________________________________________

The product from the 2nd reactor is fed to the 3rd reactor.

Temperature on entry into the 3rd reactor 490° C.

Exit temperature 434.2° C.

The other operating parameters are analogous to those in the 2ndreactor.

The composition of the feed mixture and the product on leaving the 3rdreactor is shown in Table 3.

                                      TABLE 3    __________________________________________________________________________    Composition (kmol/h)    Steam     H.sub.2                   Dry gas                       Aromatics                            Napthenes                                 n-paraffins                                      iso-paraffins    __________________________________________________________________________    Feed mixture on entry              9931.3                   2745.26                       476.68                            71.00                                 272.4                                      496.8    into the 3rd reactor    Gas mixture at the exit              10045.18                   2913.53                       519.43                            48.23                                 246.08                                      492.71    of the 3rd reactor    __________________________________________________________________________

When carrying out the process in accordance with the comparative example(gas/steam mixture flows in the direction from the circumference to thecentre of the reactor), the yield of final product is 93.86% at a MON of77.2.

EXAMPLE 2

Example 1 is repeated except that in the 2nd reactor the steam/gasmixture flows in the direction from the centre to the circumference. Thecomposition of the feed mixture on entry into the 2nd reactorcorresponds to that of Example 1. The composition of the product leavingthe 2nd reactor is shown in Table 4.

                                      TABLE 4    __________________________________________________________________________    Composition (kmol/h)    Steam     H.sub.2                  Dry gas                      Aromatics                           Napthenes                                n-paraffins                                     iso-paraffins    __________________________________________________________________________    Gas mixture at the exit              9878.6                  2749.01                      467.33                           97.7 284.3                                     504.0    of the 2nd reactor    __________________________________________________________________________

The product of the 2nd reactor is fed into the 3rd reactor which isoperated under the same conditions as in Example 1. This gives a producthaving the composition shown in Table 5.

                                      TABLE 5    __________________________________________________________________________    Composition (kmol/h)    Steam     H.sub.2                  Dry gas                      Aromatics                           Napthenes                                n-paraffins                                     iso-paraffins    __________________________________________________________________________    Gas mixture at the exit              9898.86                  2913.7                      511.89                           51.49                                249.2                                     508.82    of the 3rd reactor    __________________________________________________________________________

When carrying out the process as described in Example 2 (the steam/gasmixture in the 1st and in the 3rd reactor flows from the circumferenceto the centre of the reactor, while in the 2nd reactor it flows from thecentre of the reactor to the circumference), the yield of final productis 94.74% by mass at a MON of 78.

EXAMPLE 3

Example 2 is repeated except that the temperature on entering the 3rdreactor is 496° C. From the 3rd reactor, a product having thecomposition shown in Table 6 is drawn off.

                  TABLE 6    ______________________________________    Composition (kmol/h)    Steam       Aromatics                         Napthenes                                  n-paraffins                                         iso-paraffins    ______________________________________    Gas mixture at the exit                534.43   31.36    201.49 472.2    of the 3rd reactor    ______________________________________

The MON of the product obtained is 85.

The process of the invention thus allows, on the one hand, the yield ofpetrol of high octane number to be increased from 93.86% to 94.74% and,on the other hand, its quality to also be improved by increasing theoctane number by 8 points.

We claim:
 1. A reactor for carrying out a process for producing petrolof high octane number by catalytic reforming of a feed mixture ofhydrogen and hydrocarbons, the reactor comprising a housing (1) havingan internal and external wall surface and ports for entry of a feedmixture and exit of reformate, a hollow insert having an axis and twoends arranged in the housing clear of the external wall and the internalsurface of the housing and having an internal wall and an external wallwhich are arranged coaxially and provided with openings with both endsof the insert having openings and being fitted with covers one coverbeing in the form of an annulus and arranged between the internalsurface of the housing and the internal wall of the insert and the othercover being circular in shape and the end of the insert is able to becompletely covered, wherein the circular cover is fitted to the endnearest the entry port for the feed mixture while the annular cover isfitted to the end nearest the exit port for the reformate, and whereinthe internal wall of the insert is cylindrical in shape, with itsopenings being arranged so the distance between them in the direction ofthe axis of the insert decreases from the end nearest the entry port forthe feed mixture to the other end by a factor of 1.2-2.5.
 2. A reactorfor carrying out a process for producing petrol of high octane number bycatalytic reforming of a feed mixture of hydrogen and hydrocarbons, thereactor comprising a housing having an internal and external wallsurface and polls for entry of a feed mixture and exit of reformate, ahollow insert having an axis and two ends arranged in the housing clearof the external wall and the internal surface of the housing and havingan internal wall and an external wall which are provided with openingswith both ends of the insert having openings and being fitted withcovers one cover being in the form of an annulus and arranged betweenthe internal surface of the housing and the internal wall of the insertand the other cover being circular in shape and the end of the insert isable to be completely covered, wherein the circular cover is fitted tothe end nearest the entry port for the feed mixture while the annularcover is fitted to the end nearest the exit port for the reformate, andwherein the axial cross-sectional area surrounded by the internal wallof the insert increases in the direction of the axis of the insert fromthe end thereof nearest the entry port for the feed mixture to the otherend by a factor of 1.2-2.5.
 3. The reactor according to claim 2, whereinthe internal wall of the insert is, viewed in axial section, conical inshape.
 4. The reactor according to claim 2, wherein the internal wall ofthe insert is, viewed in axial section, in the form of steps.
 5. Thereactor according to claim 1 or 2, wherein the cover consists of atleast two parts.
 6. A process for producing petrol of high octane numberby catalytic reforming of a feed mixture of hydrogen and hydrocarbons bypassing hiss mixture through a platinum/rhenium catalyst arranged in theform of a hollow cylinder in a reactor according to claim 1 or 2,perpendicular to the cylinder axis in a direction from the cylinder axisto the circumference thereof at a temperature of at 450°-500° C., apressure of 1.5-3 MPa, and a space velocity of 1.5¹⁻ 1.8⁻¹.
 7. Theprocess according to claim 6 wherein the feed mixture is passed throughat a volume ratio of hydrogen or hydrogen-containing gas to hydrocarbonsof 1200-1800 Nm^(3/Nm) ³.